Fix for issue 25236

runtime/vm/compiler.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/block_scheduler.h"
@@ skipping 1736 matching lines @@
       queue_monitor_(new Monitor()), done_monitor_(new Monitor()),
       function_queue_(new BackgroundCompilationQueue()) {
   *done_ = false;
 }
 
 
 void BackgroundCompiler::Run() {
   while (running_) {
     // Maybe something is already in the queue, check first before waiting
     // to be notified.
-    Thread::EnterIsolateAsHelper(isolate_);
+    bool result = Thread::EnterIsolateAsHelper(isolate_);
+    ASSERT(result);
     {
       Thread* thread = Thread::Current();
       StackZone stack_zone(thread);
       Zone* zone = stack_zone.GetZone();
       HANDLESCOPE(thread);
       Function& function = Function::Handle(zone);
       function = function_queue()->PeekFunction();
       while (running_ && !function.IsNull()) {
         const Error& error = Error::Handle(zone,
             Compiler::CompileOptimizedFunction(thread,
@@ skipping 208 matching lines @@
 }
 
 
 void BackgroundCompiler::EnsureInit(Thread* thread) {
   UNREACHABLE();
 }
 
 #endif  // DART_PRECOMPILED
 
 }  // namespace dart